8295407: C2 crash: Error: ShouldNotReachHere() in multiple vector tests with -XX:-MonomorphicArrayCheck -XX:-UncommonNullCast #11034

fg1417 · 2022-11-08T02:36:13Z

For unsupported CMove patterns, JDK-8293833 helps remove unused CMove and related packs from superword candidate packset by the function remove_cmove_and_related_packs(), but it only works when -XX:+UseVectorCmov is enabled[1]. When the option is not enabled, these unsupported CMove packs are still kept in the superword packset, causing the same failure.

Actually, the function filter_packs() in superword is to filter out unsupported packs but it can't work as expected currently for these CMove cases. As we know, not all CMove packs can be vectorized. merge_packs_to_cmovd()[2] looks through all packs in the superword packset and generates a CMove candidate packset to collect all qualified CMove packs. Hence, only CMove packs in the CMove candidate packset are our target patterns and can be vectorized. But filter_packs() thinks, if the CMove pack is in a superword packset and its vector node is implemented in the current platform, then it can be vectorized. Therefore, the function doesn't remove these unsupported packs.

We can adjust the function implemented() in the stage of filter_packs() to check if the current CMove pack is in the CMove candidate packset. If not, filter_packs() considers it not to be vectorized and then remove it. After the fix, whether
-XX:+UseVectorCmov is enabled or not, these unsupported packs can be removed by filter_packs(). In this way, we don't need the functionremove_cmove_and_related_packs() anymore and thus the patch also cleans related code.

[1]

jdk/src/hotspot/share/opto/superword.cpp

Line 537 in 9b9be88

if (UseVectorCmov) {

[2]

jdk/src/hotspot/share/opto/superword.cpp

Line 1892 in 9b9be88

_cmovev_kit.make_cmove_pack(pk);

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Issue

JDK-8295407: C2 crash: Error: ShouldNotReachHere() in multiple vector tests with -XX:-MonomorphicArrayCheck -XX:-UncommonNullCast

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Tobias Hartmann (@TobiHartmann - Reviewer)
Vladimir Kozlov (@vnkozlov - Reviewer)

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…ts with -XX:-MonomorphicArrayCheck -XX:-UncommonNullCast For unsupported `CMove` patterns, JDK-8293833 helps remove unused `CMove` and related packs from superword candidate packset by the function `remove_cmove_and_related_packs()`, but it only works when `-XX:+UseVectorCmov` is enabled[1]. When the option is not enabled, these unsupported `CMove` packs are still kept in the superword packset, causing the same failure. Actually, the function `filter_packs()` in superword is to filter out unsupported packs but it can't work as expected currently for these `CMove` cases. As we know, not all `CMove` packs can be vectorized. `merge_packs_to_cmovd()`[2] looks through all packs in the superword packset and generates a `CMove` candidate packset to collect all qualified `CMove` packs. Hence, only `CMove` packs in the `CMove` candidate packset are our target patterns and can be vectorized. But `filter_packs()` thinks, if the `CMove` pack is in a superword packset and its vector node is implemented in the current platform, then it can be vectorized. Therefore, the function doesn't remove these unsupported packs. We can adjust the function `implemented()` in the stage of `filter_packs()` to check if the current `CMove` pack is in the `CMove` candidate packset. If not, `filter_packs()` considers it not to be vectorized and then remove it. After the fix, whether `-XX:+UseVectorCmov` is enabled or not, these unsupported packs can be removed by `filter_packs()`. In this way, we don't need the function`remove_cmove_and_related_packs()` anymore and thus the patch also cleans related code. [1] https://github.com/openjdk/jdk/blob/9b9be88bcaa35c89b6915ff0c251e5a04b10b330/src/hotspot/share/opto/superword.cpp#L537 [2] https://github.com/openjdk/jdk/blob/9b9be88bcaa35c89b6915ff0c251e5a04b10b330/src/hotspot/share/opto/superword.cpp#L1892 [3] https://github.com/openjdk/jdk/blob/9b9be88bcaa35c89b6915ff0c251e5a04b10b330/src/hotspot/share/opto/superword.cpp#L2701

bridgekeeper · 2022-11-08T02:38:14Z

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openjdk · 2022-11-08T02:41:33Z

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mlbridge · 2022-11-08T02:46:09Z

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01: Full - Incremental (bcf6a21e)
00: Full (97a27264)

TobiHartmann

Looks good to me otherwise but someone more familiar with superword should look at this as well.

TobiHartmann · 2022-11-11T08:38:34Z

test/hotspot/jtreg/compiler/loopopts/TestUnsupportedConditionalMove.java

+ * @test
+ * @bug 8295407
+ * @summary C2 crash: Error: ShouldNotReachHere() in multiple vector tests with
+ *          -XX:-MonomorphicArrayCheck -XX:-UncommonNullCast


MonomorphicArrayCheck and UncommonNullCast are debug flags, the test will fail with a release build.

@TobiHartmann, thanks for your review! The options added here is commented as part of summary title, not as JVM options. I suppose it should be fine for a release build, right? :-)

Right, I missed that. Does the test reproduce the issue without these flags? In any case, I think a more descriptive summary would be good.

Yes, the added testcase here can reproduce the issue even without these flags and I suppose those flags help C2 vectorize more hot loops in the reported testcases. I updated the summary part in the new commit. Thanks for your suggestion @TobiHartmann!

Great, thanks for confirming and updating the summary!

vnkozlov

I have request since you are touching this code.
8192846 changes were a little sloppy and did not rename some methods which causing confusion.
Please, rename is_CmpD_candidate, merge_packs_to_cmpd and others you find to general fp as you did with is_cmove_fo_opcode.

vnkozlov · 2022-11-14T23:01:50Z

Or may be simply remove D: is_Cmp_candidate(), merge_packs_to_cmove(), test_cmp_pack().
There are also comments which describes only CMoveD.

vnkozlov · 2022-11-14T23:02:50Z

Do we have IR tests to verify cmove vectorization?

fg1417 · 2022-11-16T02:16:20Z

I have request since you are touching this code. 8192846 changes were a little sloppy and did not rename some methods which causing confusion. Please, rename is_CmpD_candidate, merge_packs_to_cmpd and others you find to general fp as you did with is_cmove_fo_opcode.
Or may be simply remove D: is_Cmp_candidate(), merge_packs_to_cmove(), test_cmp_pack(). There are also comments which describes only CMoveD.

@vnkozlov, thanks for point it out. I cleaned up related code and comments in the new commit. Could you please help review it? Thanks!

Do we have IR tests to verify cmove vectorization?

Yes, we do. I added compiler/c2/irTests/TestVectorConditionalMove.java in JDK-8289422.

vnkozlov

Looks good. I submitted testing.

TobiHartmann

Looks good to me. Let's wait for Vladimir's testing to finish.

openjdk · 2022-11-16T06:06:29Z

@fg1417 This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8295407: C2 crash: Error: ShouldNotReachHere() in multiple vector tests with -XX:-MonomorphicArrayCheck -XX:-UncommonNullCast

Reviewed-by: thartmann, kvn

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At the time when this comment was updated there had been 70 new commits pushed to the master branch:

e2269fd: 8296968: Update langtools tests to use @enablePreview
2159170: 8296453: Simplify resource_area uses in ClassPathDirEntry::open_stream
95c390e: 8296956: [JVMCI] HotSpotResolvedJavaFieldImpl.getIndex returns wrong value
68d3ed5: 8296442: EncryptedPrivateKeyInfo can be created with an uninitialized AlgorithmParameters
37848a9: 8296967: [JVMCI] rationalize relationship between getCodeSize and getCode in ResolvedJavaMethod
b3ef337: 8296960: [JVMCI] list HotSpotConstantPool.loadReferencedType to ConstantPool
f0474b8: 8283238: make/scripts/compare.sh should show the diff when classlist does not match
04a4d34: 8297006: JFR: AbstractEventStream should not hold thread instance
5db1b58: 8296961: [JVMCI] Access to j.l.r.Method/Constructor/Field for ResolvedJavaMethod/ResolvedJavaField
4ce4f38: 8296958: [JVMCI] add API for retrieving ConstantValue attributes
... and 60 more: https://git.openjdk.org/jdk/compare/8eb90e2d9c4ab5975f4301dbfdb0a6d9fa036af3...master

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vnkozlov · 2022-11-16T07:30:52Z

I got 2 failures. Description in the bug report. One could be not related. But Vector512ConversionTests.java test failure with flags from the bug report is suspicious.

vnkozlov · 2022-11-16T07:38:43Z

Digging in JBS shows that Vector512ConversionTests.java failure is most likely JDK-8276064. So it is not new failure.

Looks like your changes are fine.

fg1417 · 2022-11-17T01:29:51Z

Thanks for your kind review and test work, @TobiHartmann @vnkozlov. I'll integrate it.

/integrate

openjdk · 2022-11-17T01:31:21Z

@fg1417
Your change (at version bcf6a21) is now ready to be sponsored by a Committer.

pfustc · 2022-11-17T01:37:57Z

/sponsor

openjdk · 2022-11-17T01:40:13Z

Going to push as commit cc44419.
Since your change was applied there have been 70 commits pushed to the master branch:

e2269fd: 8296968: Update langtools tests to use @enablePreview
2159170: 8296453: Simplify resource_area uses in ClassPathDirEntry::open_stream
95c390e: 8296956: [JVMCI] HotSpotResolvedJavaFieldImpl.getIndex returns wrong value
68d3ed5: 8296442: EncryptedPrivateKeyInfo can be created with an uninitialized AlgorithmParameters
37848a9: 8296967: [JVMCI] rationalize relationship between getCodeSize and getCode in ResolvedJavaMethod
b3ef337: 8296960: [JVMCI] list HotSpotConstantPool.loadReferencedType to ConstantPool
f0474b8: 8283238: make/scripts/compare.sh should show the diff when classlist does not match
04a4d34: 8297006: JFR: AbstractEventStream should not hold thread instance
5db1b58: 8296961: [JVMCI] Access to j.l.r.Method/Constructor/Field for ResolvedJavaMethod/ResolvedJavaField
4ce4f38: 8296958: [JVMCI] add API for retrieving ConstantValue attributes
... and 60 more: https://git.openjdk.org/jdk/compare/8eb90e2d9c4ab5975f4301dbfdb0a6d9fa036af3...master

Your commit was automatically rebased without conflicts.

openjdk · 2022-11-17T01:40:44Z

@pfustc @fg1417 Pushed as commit cc44419.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

openjdk bot added the rfr Pull request is ready for review label Nov 8, 2022

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Fei Gao added 2 commits November 16, 2022 01:33

Merge branch 'master' into fg8295407

7fc87c0

Clean up related code

bcf6a21

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8295407: C2 crash: Error: ShouldNotReachHere() in multiple vector tests with -XX:-MonomorphicArrayCheck -XX:-UncommonNullCast #11034

8295407: C2 crash: Error: ShouldNotReachHere() in multiple vector tests with -XX:-MonomorphicArrayCheck -XX:-UncommonNullCast #11034

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8295407: C2 crash: Error: ShouldNotReachHere() in multiple vector tests with -XX:-MonomorphicArrayCheck -XX:-UncommonNullCast #11034

8295407: C2 crash: Error: ShouldNotReachHere() in multiple vector tests with -XX:-MonomorphicArrayCheck -XX:-UncommonNullCast #11034

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